Process for the manufacture of tolidine



Patented 55.25, 1941 UNITED STATES 2,233,121 PROCESS FOR. THE MANUFACTURE OF TOLIDINE Clyde 0. Henke, Wilmington, DeL, and Roland G. Benner, Carney: Point, N. 1., auignors to E. I. du Pont de Nemours a Company, Wilmington, Del, a corporation of Delaware No Drawing. Application November 8, 1939,

Serial No. 303,41

. 7Claims.

1 This invention relates to a process for the manufacture of tolidine and, more particularly, to the production of tolidine from o-nitrotoiuene by catalytic hydrogenation in the liquid phase.

' 5 Tolidine has heretofore been produced on a commercial scale by reduction of o-nitrotoluene with zinc dust and caustic soda to hydrazotoluene. which is inverted to tolidine by dilute acids. Although fairly good yields of tolidine areobtainm able by this method,the cost of production has been high because of thehigh cost of zinc dust and'the expense resulting from difllculties involved in separating the zinc sludge from the reductlon mass. I

7 Hydrogen has been found to be more economical for reduction of many nitro bodies to the amines than either of the older methods which involve the use or zinc or iron. However, no method hasbeen previously developed for the 10 production of tolidine from o-nitrotoluene with hydrogen.

Nitrobenzene has been reduced with hydrogen,

mum presence of a nickel catalyst and caustic soda; tdazobenzene and hydrazobenzene, which 35, can be' converted to benzidine by known methods.

However, this method is not satisfactory for the manufacture of tolidine from o-nitrotoluene as very low yields of tolidine are obtained.

The present invention has as an obiect'an improved andeconomical process for the production of tolidine. A further object is the production of' dium'and'in anuoiygen-containing, non-acidic,

40 organic solvent having from 1 to 7 carbon atoms.

o-Nitrotoluene is reduced at temperatures below 150 C. andat hydrogen pressures above one atmosphere, in an oxygen-containing, non-acidic, organic solvent of from 1 through '7 carbon atoms,

. in'the presence of an active noble metal catalyst,

and in an alkaline medium to a mixture of hydrazotoluene. o-toluidine, and a small amount of azotoluene. The mixture is treated with hydrochloric acid and iron to convert the azo-hydrazoso toluene to tolidine hydrochloride andto convert the o-toluidlne to its hydrochloride. The o-toluldine hydrochloride is separated from the tolidine hydrochloride by filtration, converted to o-toluldine by the addition of'lime, and distilled. The tolidine hydrochloride is washed free of isomers,

(e1. sec -47s) o-toluidine, and solvent, and is converted to tolidine by soda ash. i w

The following examples set. forth certain well defined instances of the application of this invention. They are, however, not to be considered as 8 limitations thereof, since many modifications may be made without departing from the spirit-and scope of this invention.

Example I In an iron autoclave equipped for rapid agitation are charged 100 parts ,of o-nitrotoluene, 150 parts of the azeotropic mixture of .isopropanol and water, 9 parts of caustic soda, and 0.030 part of palladium black supported on activated carbon. The charge is hydrogenated. at to C. and under 100 to200 lbs. per sq. in. hydrogen pressure. The absorption of hydrogen is continued until it becomes very slow. The hydrogenated mass is then taken from the autoclave, the autoclave washed, and the washings combined with the mass. The charge is then cooled to 20 to 30 C. Water is added and the mixture is cooled to 0* to 5 C. -While this temperature is maintained, 180 parts of 33% hydrochloric acid are 25 added to invert the hydrazotoluene to tolidine hydrochloride. After agitating for 4 hours at this temperature, 5 parts of iron powder are added. For 2 hours the agitation iscontinued at 0 to 5 C. Thetemperature is then gradually m raised to 30 C. over a period of about 3 hours. After 4 to 5 hours agitation" at this temperature, the mass becomes gray and 65 parts of salt are added. The tolidine hydrochlorideis then filtered out and washed with 200 parts of cold 15% salt solution. The filtrate is made alkaline and is then steam-distilled to recover the isopropanol and o-toluidine. The tolidine hydrochloride is dissolved in boiling water and is filtered at 100 v 100 parts of salt are added. The tolidine hydrochloride, which crystallizes out, is filtered and washed with 100 parts of cold 15% salt solution. 5 The mass is then slurried in water and is converted to tolidine by the addition of soda ash until the slurry is alkaline. The slurry is then cooled to 20 to 25 C., filtered, and the cake. washed with cold water. The tolidine is dried at to C. under vacuum. The material is white and has a freezing point of above 128.0 C. Yields of 60 to 70% of theory of tolidine are obtained.. In addition, a yield of 20 to 25% of theory of o-toluidine is obtained. u

I tion are charged 100 parts of o-nitrotoluene, 150' Example II In an iron autoclave equipped for rapid agitation are charged 100 parts or o-nitrotoluene, 150 parts ot'isopropanol, 15 parts of soda ash, and

0.030 part of platinum black supported on acti-.

vated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o-toiuidine in a manner similar to Example I.

" Example III In an iron autoclave equipped for rapid agitation are charged 100 parts of o-nitrotoiuene, 150 parts of ethanol, 9 parts of caustic soda, and 0.050 part of palladium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o-toluidine in a manner similar to Example I.

Example IV In an iron autoclave equipped for rapid agitation are charged 100 parts'oi o-nitrotoluene, 150 parts of acetone, 9 parts of caustic soda, and 0.050 part or palladium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o-toluidine in a manner similar to Example Example V In an iron autoclave equipped for rapid agitation are charged 100 parts or o-nitrotoluene, 200 parts or the azeotropic mixture ,of isopropahol and water, 3 parts 01' caustic soda, and 0.030 part of palladium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o,- toluidine ina manner similar to Example I.

Example VII In an iron autoclave equipped for rapid agitaparts of isopropanol, 6 parts of caustic soda, and 0.030 part of rhodium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o-toluidine in a manner similar to Example I.

" Example VIII In an iron autoclave equipped for rapid agitation are charged 100 parts of o-nitrotoluene, 67 parts of the azeotropic mixture oi. isopropanol and water, 2 parts of caustic soda, and 0.030 part of palladium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidineand o-toluidine in a manner similar to Example I.

Eraniple IX In an iron autoclave equipped for rapid agitation are charged 100 parts of o-nitrotoluene, 150 parts 01 the azeotropic mixture of isopropanol and water, 9-parts of caustic soda, and 0.015 part of palladium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o-toluidine in a manner similar to ExampleI.

Example X In an iron autoclave equipped for rapid agitation are'charged 100 parts of o-nitrotoluene, 50 parts or the azeotropic mixture or isopropanol and water, 4.5 parts of caustic soda, and 0.020 part oi palladium black supported on activated carbon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and otoluidine in a manner similar to Example I.

Example X] In an iron autoclave equipped for rapid agitation are charged 100 parts of o-nitrotoiuene, 200

parts of the azeotropic mixture of isopropanol and water, 6 parts of caustic soda, and 0.080 part, of palladium black supported on activated car-- bon. The charge is hydrogenated and the hydrogenated mass is converted to tolidine and o-toluidine in a manner similar to Example I.

This invention is not limited to the particular conditions cited in the above examples.

The rate of reaction is greatly influenced by the temperature, higher temperatures increasing the reduction rate, but better yields are obtained within the range of to C. However, the

hydrogenation may be carried out from 30 to although higher yields are obtained with isopropanol. The solvent should be an oxygen-containing, non-acidic, organic compound of from 1 through '7 carbon atoms. This would include all aliphatic, cyclic, and aromatic alcohols, ketones.

' aldehydes, esters, and ethers of from 1 through 7 carbons. While ethers fall into this category, the hazards involved in their use make it inadvisable to employ them. Mixtures of the above solvents or materials resulting in the formation of them are included. Examples of these are: methanol, ethanol, n-propanol, isopropanol, n-butanol, secondary-butanol, isobu'tanol, tertiary-butanol, namyl alcohol, isoamyl alcohol, tertiary-amyl alcohol, iusel oil, Pentasol (a commercial mixture of amyl alcohols), n-hexanol, acetone, methyl ethyl ketone, diethyl ketone, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, cyclohexanol, benzyl alcohol, etc.

The amount or catalyst employed is preferably between 0.005 and 0.050% based on the weight of nitro body, but may be decreasedas long as it shows activity, or increased, as desired. The 'use of more than 0.5% noble metal in the catalyst, based on the nitrotoluene, makes the process impractical due to the cost'of the metal. The

catalyst may be palladium black, platinum black or rhodium black and is preferably prepared in accordance with U. S. application Serial No. 303,475, illed 01' even date herewith. However, the noble metal compounds may be used, as well as mixtures or other physical forms oi! the metals, such as colloids and the like. They are preferably terial decreases the rate of reduction.

supported on activated carbon but they may be unsupported or supported on any inert carrier such as, for example, charcoal, kieselguhr, asbestos, fuller's earth, filtercel, bentonite, vermiculite, monox, silica, and the like. The catalyst may be recovered by filtering the autoclave charge or it may be filtered off with the unreacted iron after the inversion is completed.

The alkaline material is preferably caustic soda in amountsoi 2-to .10% of the weight of o-nltrotol'uene, but the proportionmay' be varied from 0.5 to 50% or more of the weight 0! nitro body. The equivalent of any material resulting in an alkaline medium under the conditions employed may also be used. Lower alkalinitydecreases the yield of tolidine; more alkaline ma- The most common alkaline materials are the oxides, hydroxides. salts of weak acids, alcoholates, and phenolates oi the alkali and of the alkaline earth metals, as well as strong organic bases or salts, various compounds of the nitrogen system, and various compounds of other metals, such as magnesium. Examples of the above are: sodium hydroxide, potassium hydroxide. calcium hydroxide, barium hydroxide, strontium, hydroxide, ammoy nium hydroxide, sodium carbonate, potassium carbonate, sodium oxide. potassium oxide, calcium oxide, barium oxide, strontium oxide, sodium acetate, potassium acetate, calcium acetate, barium acetate, strontium acetate, sodium stearate, potassium stearate, sodium silicates, potassium silicates, trisodium phosphate, tripotassium phosphate. etc. Free alkali and alkaline earth metals will react to produce an alkaline medium. The essential detail is that the charge to be bydrogenated should be in an alkaline medium.

Water may or may not be present in the charge,

to behydrogenated. If water is to be present, it"

may be added separately or by means of an aqueous solution 01' the solvent or of the alkaline material.

The aceotropic mixture oi! isopropanol and water cited in some or the examples contains about 88% isopropanoi.

The hydrogen employed is preferably electrolytic hydrogen gas but may be obtained irom any other source, and gases in which hydrogen is present, such as water-gas, may be used.

By the preceding methods, tolidine oi exceptionally high purity is obtainable with considerable more economy than byprevious commercial methods. Yields up to of theory of tolidine .are obtainable with o-toluidine as a valuable shy-product. At least to of theory of useful products is obtainable.

V 7 It is apparent that many widely diflferent embodiments of this invention may be made without departing from the spirit and scope thereof and therefore it is not intended to be limited except "as indicated in the appended'claims.

characterized in that the organic solvent is an aliphatic alcohol.

4. The process in accordance with claim 1 characterized in that the organic solvent is isopropanol.

5. The process in accordance with claim 1 characterized in that thecatalyst is a palladium catalyst.

6. The process in accordance with claim 1 characterized in that the alkaline medium is a sodium hydroxide medium.

'1. The process which comprises catalytically hydrogenating o-nitrotoluenein the presence or a palladium catalyst, in isopropyl alcohol, and in a sodium hydroxide medium at a temperature within the range of 30" to C.

CLYDE O. HENKE. ROLAND G. BENNER. 

